New Zealand soldiers liberated the town from the Germans in 1918 by scaling its wall.

"We were there about three days ago, and we saw them preparing for this - putting up France's flag, New Zealand flags, all around the streets in the town centre," Colonel Krushka said.

"Then when we were there today, an absolutely fantastic turn-out from the locals and we really felt well supported."

He said those in Europe appreciated the scale of New Zealand's commitment relative to its size.

"They realise how much we as a small nation have committed over here, and the huge casualty rate that we had."

An Australian soldier stands in front of the Cenotaph following a dawn service in Sydney. Photo: AFP

In the UK, Prince Harry was expected to attend three Anzac Day commemoration services in London.

The events, organised by the New Zealand and Australian High commissions, include a dawn service at Wellington Arch, a wreath-laying ceremony and parade at the Cenotaph, and a service of commemoration and thanksgiving at Westminster Abbey.

Anzac Day has been officially commemorated in the city since the first anniversary of the Anzac landings at Gallipoli in Turkey in 1916, when King George attended a service at the abbey.

Hundreds gather at Gallipoli

Thunder, lightning and rain greeted New Zealanders and Australians arriving for this year's memorial event at Anzac Cove in Gallipoli.

More than 1000 people were understood to have gathered for an overnight vigil and reflective programme, followed by today's dawn service.

Visitors then started the 6km walk from the beach up to Chunuk Bair for the New Zealand service.

Hundreds of New Zealanders and Australians stationed in Iraq, meanwhile, joined an Anzac Day ceremony on their base in Taji, northwest of Baghdad.

The soldiers - more than 100 New Zealanders and 300 Australians - are part of a combined mission to train the Iraqi Security Forces.

Observers said today's service was particularly poignant for the soldiers, who were part of the largest joint New Zealand and Australian taskforce to the Middle East since Gallipoli.

After the dawn service, soldiers had a customary "gunfire breakfast" - but without the traditional ration of rum in their coffee, due to an alcohol ban reportedly imposed by the New Zealand command.

Anzac Day 2016 at Camp Taji, Iraq Photo: Twitter / @nznavy

Photo: Twitter / @nznavy

Soldiers from both countries will tonight cram around a solitary television set to watch the annual clash between St George Illawarra and the Sydney Roosters, and the other games in the NRL's Anzac Day triple-header.

Fallen also remembered in Jakarta

Australians and New Zealanders also gathered in Jakarta for a dawn service to recommemorate past and present serviceman.

The gathering remembered those who died in defence of Java and Sumatra during the Japanese advance in 1942, and also those held for years by the Japanese.

This included 65 army nurses, who were evacuated from Singapore in February 1942.

Their ship was bombed and sunk, and 33 of them were lost at sea or rescued then executed by the Japanese.

The rest spent three and a half years as prisoners of war.

Wet weather cleared towards the end of this morning's event at Anzac Cove. Photo: AFP

People line up to pay their respects at the dawn service in Melbourne. Photo: AFP